Multiple improvements to selectors.

* Added ``getFd`` procedure for retrieving the underlying
  selector's FD.
* Selectors module's procedures now accept an ``int`` as well as a
  ``SocketHandle``.
* ReadyKey now contains the error code for Event.Error events.

changelog.md

@@ -16,6 +16,8 @@
 
 ### Library changes
 
+- The `ReadyKey` type in the selectors module now contains an ``errorCode``
+  field to help distinguish between ``Event.Error`` events.
 - The `AsyncFD` type now reflects the fact that the underlying FD is registered
   in the async dispatcher.
 - The overloading rules changed slightly so that constrained generics are

lib/pure/ioselects/ioselectors_epoll.nim

@@ -141,7 +141,7 @@ template checkFd(s, f) =
   if f >= s.maxFD:
     raiseIOSelectorsError("Maximum number of descriptors is exhausted!")
 
-proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
+proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
                         events: set[Event], data: T) =
   let fdi = int(fd)
   s.checkFd(fdi)
@@ -156,7 +156,7 @@ proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
       raiseIOSelectorsError(osLastError())
     inc(s.count)
 
-proc updateHandle*[T](s: Selector[T], fd: SocketHandle, events: set[Event]) =
+proc updateHandle*[T](s: Selector[T], fd: int | SocketHandle, events: set[Event]) =
   let maskEvents = {Event.Timer, Event.Signal, Event.Process, Event.Vnode,
                     Event.User, Event.Oneshot, Event.Error}
   let fdi = int(fd)
@@ -391,9 +391,19 @@ proc selectInto*[T](s: Selector[T], timeout: int,
       let pevents = resTable[i].events
       var pkey = addr(s.fds[fdi])
       doAssert(pkey.ident != 0)
-      var rkey = ReadyKey(fd: int(fdi), events: {})
+      var rkey = ReadyKey(fd: fdi, events: {})
 
       if (pevents and EPOLLERR) != 0 or (pevents and EPOLLHUP) != 0:
+        if (pevents and EPOLLHUP) != 0:
+          rkey.errorCode = ECONNRESET.OSErrorCode
+        else:
+          # Try reading SO_ERROR from fd.
+          var error: cint
+          var size = sizeof(error).SockLen
+          if getsockopt(fdi.SocketHandle, SOL_SOCKET, SO_ERROR, addr(error),
+                        addr(size)) == 0'i32:
+            rkey.errorCode = error.OSErrorCode
+
         rkey.events.incl(Event.Error)
       if (pevents and EPOLLOUT) != 0:
         rkey.events.incl(Event.Write)
@@ -481,7 +491,7 @@ template isEmpty*[T](s: Selector[T]): bool =
   (s.count == 0)
 
 proc contains*[T](s: Selector[T], fd: SocketHandle|int): bool {.inline.} =
-  return s.fds[fd].ident != 0
+  return s.fds[fd.int].ident != 0
 
 proc getData*[T](s: Selector[T], fd: SocketHandle|int): var T =
   let fdi = int(fd)
@@ -515,3 +525,6 @@ template withData*[T](s: Selector[T], fd: SocketHandle|int, value, body1,
     body1
   else:
     body2
+
+proc getFd*[T](s: Selector[T]): int =
+  return s.epollFd.int

lib/pure/ioselects/ioselectors_kqueue.nim

@@ -217,7 +217,7 @@ else:
           raiseIOSelectorsError(osLastError())
         s.changes.setLen(0)
 
-proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
+proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
                         events: set[Event], data: T) =
   let fdi = int(fd)
   s.checkFd(fdi)
@@ -235,7 +235,7 @@ proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
     when not declared(CACHE_EVENTS):
       flushKQueue(s)
 
-proc updateHandle*[T](s: Selector[T], fd: SocketHandle,
+proc updateHandle*[T](s: Selector[T], fd: int | SocketHandle,
                       events: set[Event]) =
   let maskEvents = {Event.Timer, Event.Signal, Event.Process, Event.Vnode,
                     Event.User, Event.Oneshot, Event.Error}
@@ -503,6 +503,7 @@ proc selectInto*[T](s: Selector[T], timeout: int,
 
       if (kevent.flags and EV_ERROR) != 0:
         rkey.events = {Event.Error}
+        rkey.errorCode = kevent.data.OSErrorCode
 
       case kevent.filter:
       of EVFILT_READ:
@@ -569,6 +570,13 @@ proc selectInto*[T](s: Selector[T], timeout: int,
         doAssert(true, "Unsupported kqueue filter in the queue!")
 
       if (kevent.flags and EV_EOF) != 0:
+        if kevent.fflags != 0:
+          rkey.errorCode = kevent.fflags.OSErrorCode
+        else:
+          # This assumes we are dealing with sockets.
+          # TODO: For future-proofing it might be a good idea to give the
+          #       user access to the raw `kevent`.
+          rkey.errorCode = ECONNRESET.OSErrorCode
         rkey.events.incl(Event.Error)
 
       results[k] = rkey
@@ -585,7 +593,7 @@ template isEmpty*[T](s: Selector[T]): bool =
   (s.count == 0)
 
 proc contains*[T](s: Selector[T], fd: SocketHandle|int): bool {.inline.} =
-  return s.fds[fd].ident != 0
+  return s.fds[fd.int].ident != 0
 
 proc getData*[T](s: Selector[T], fd: SocketHandle|int): var T =
   let fdi = int(fd)
@@ -619,3 +627,7 @@ template withData*[T](s: Selector[T], fd: SocketHandle|int, value, body1,
     body1
   else:
     body2
+
+
+proc getFd*[T](s: Selector[T]): int =
+  return s.kqFD.int

lib/pure/ioselects/ioselectors_poll.nim

@@ -141,7 +141,7 @@ template checkFd(s, f) =
   if f >= s.maxFD:
     raiseIOSelectorsError("Maximum number of descriptors is exhausted!")
 
-proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
+proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
                         events: set[Event], data: T) =
   var fdi = int(fd)
   s.checkFd(fdi)
@@ -149,7 +149,7 @@ proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
   setKey(s, fdi, events, 0, data)
   if events != {}: s.pollAdd(fdi.cint, events)
 
-proc updateHandle*[T](s: Selector[T], fd: SocketHandle,
+proc updateHandle*[T](s: Selector[T], fd: int | SocketHandle,
                       events: set[Event]) =
   let maskEvents = {Event.Timer, Event.Signal, Event.Process, Event.Vnode,
                     Event.User, Event.Oneshot, Event.Error}
@@ -280,7 +280,7 @@ template isEmpty*[T](s: Selector[T]): bool =
   (s.count == 0)
 
 proc contains*[T](s: Selector[T], fd: SocketHandle|int): bool {.inline.} =
-  return s.fds[fd].ident != 0
+  return s.fds[fd.int].ident != 0
 
 proc getData*[T](s: Selector[T], fd: SocketHandle|int): var T =
   let fdi = int(fd)
@@ -314,3 +314,7 @@ template withData*[T](s: Selector[T], fd: SocketHandle|int, value, body1,
     body1
   else:
     body2
+
+
+proc getFd*[T](s: Selector[T]): int =
+  return -1

lib/pure/ioselects/ioselectors_select.nim

@@ -229,7 +229,7 @@ proc delKey[T](s: Selector[T], fd: SocketHandle) =
   doAssert(i < FD_SETSIZE,
            "Descriptor [" & $int(fd) & "] is not registered in the queue!")
 
-proc registerHandle*[T](s: Selector[T], fd: SocketHandle,
+proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
                         events: set[Event], data: T) =
   when not defined(windows):
     let fdi = int(fd)
@@ -255,7 +255,7 @@ proc registerEvent*[T](s: Selector[T], ev: SelectEvent, data: T) =
     IOFD_SET(ev.rsock, addr s.rSet)
     inc(s.count)
 
-proc updateHandle*[T](s: Selector[T], fd: SocketHandle,
+proc updateHandle*[T](s: Selector[T], fd: int | SocketHandle,
                       events: set[Event]) =
   let maskEvents = {Event.Timer, Event.Signal, Event.Process, Event.Vnode,
                     Event.User, Event.Oneshot, Event.Error}
@@ -279,7 +279,7 @@ proc updateHandle*[T](s: Selector[T], fd: SocketHandle,
         inc(s.count)
       pkey.events = events
 
-proc unregister*[T](s: Selector[T], fd: SocketHandle) =
+proc unregister*[T](s: Selector[T], fd: int | SocketHandle) =
   s.withSelectLock():
     var pkey = s.getKey(fd)
     if Event.Read in pkey.events:
@@ -451,3 +451,6 @@ template withData*[T](s: Selector[T], fd: SocketHandle|int, value,
     else:
       body2
 
+
+proc getFd*[T](s: Selector[T]): int =
+  return -1

lib/pure/selectors.nim

@@ -54,9 +54,9 @@ when defined(nimdoc):
       Timer,       ## Timer descriptor is completed
       Signal,      ## Signal is raised
       Process,     ## Process is finished
-      Vnode,       ## BSD specific file change happens
+      Vnode,       ## BSD specific file change
       User,        ## User event is raised
-      Error,       ## Error happens while waiting, for descriptor
+      Error,       ## Error occurred while waiting for descriptor
       VnodeWrite,  ## NOTE_WRITE (BSD specific, write to file occurred)
       VnodeDelete, ## NOTE_DELETE (BSD specific, unlink of file occurred)
       VnodeExtend, ## NOTE_EXTEND (BSD specific, file extended)
@@ -69,6 +69,8 @@ when defined(nimdoc):
       ## An object which holds result for descriptor
       fd* : int ## file/socket descriptor
       events*: set[Event] ## set of events
+      errorCode*: OSErrorCode ## additional error code information for
+                              ## Error events
 
     SelectEvent* = object
       ## An object which holds user defined event
@@ -79,13 +81,14 @@ when defined(nimdoc):
   proc close*[T](s: Selector[T]) =
     ## Closes the selector.
 
-  proc registerHandle*[T](s: Selector[T], fd: SocketHandle, events: set[Event],
+  proc registerHandle*[T](s: Selector[T], fd: int | SocketHandle,
-                          data: T) =
+                          events: set[Event], data: T) =
     ## Registers file/socket descriptor ``fd`` to selector ``s``
     ## with events set in ``events``. The ``data`` is application-defined
     ## data, which will be passed when an event is triggered.
 
-  proc updateHandle*[T](s: Selector[T], fd: SocketHandle, events: set[Event]) =
+  proc updateHandle*[T](s: Selector[T], fd: int | SocketHandle,
+                        events: set[Event]) =
     ## Update file/socket descriptor ``fd``, registered in selector
     ## ``s`` with new events set ``event``.
 
@@ -221,11 +224,15 @@ when defined(nimdoc):
   proc contains*[T](s: Selector[T], fd: SocketHandle|int): bool {.inline.} =
     ## Determines whether selector contains a file descriptor.
 
+  proc getFd*[T](s: Selector[T]): int =
+    ## Retrieves the underlying selector's file descriptor.
+    ##
+    ## For *poll* and *select* selectors ``-1`` is returned.
+
 else:
   when hasThreadSupport:
     import locks
 
-
     type
       SharedArray[T] = UncheckedArray[T]
 
@@ -234,7 +241,6 @@ else:
 
     proc deallocSharedArray[T](sa: ptr SharedArray[T]) =
       deallocShared(cast[pointer](sa))
-
   type
     Event* {.pure.} = enum
       Read, Write, Timer, Signal, Process, Vnode, User, Error, Oneshot,
@@ -247,6 +253,7 @@ else:
     ReadyKey* = object
       fd* : int
       events*: set[Event]
+      errorCode*: OSErrorCode
 
     SelectorKey[T] = object
       ident: int
@@ -264,7 +271,7 @@ else:
       msg.add("Internal Error\n")
     var err = newException(IOSelectorsException, msg)
     raise err
-
+  
   proc setNonBlocking(fd: cint) {.inline.} =
     setBlocking(fd.SocketHandle, false)